1Preheat oven to 180°C (approximately 350°F).
2Cook pasta in plenty of boiling, salted water and a drizzle of olive oil.
3Melt butter in a saucepan and heat until lightly browned.
4Add flour and stir until golden.
5Slowly stir in milk, stirring constantly with a wire whisk.
6Bring to boil and continue to stir constantly.
7Cook until mixture thickens slightly and mix in cream.
8Remove from heat and add egg yolks.
9Season with salt, pepper and a pinch of nutmeg.
10Add tuna and mix well.
11Drain the pasta and rinse in cold water.
12Drain again and pasta to pan with tuna and sauce.
14Spread a layer of pasta mixture in the bottom of a baking dish and sprinkle with grated cheese.
15Cover with another layer of pasta and repeat steps until there are no ingredients left, ending with grated cheese.
16Arrange small pieces of butter over the surface.
17Bake in preheated oven until cheese is hot and bubbly, for about 10-15 minutes.